This invention relates to arrangements for determining the distance of objects using ultrasonic transducers, to a method for producing such transducer arrangements and to distance-determining arrangements in a motor vehicle.
U.S. Pat. No. 4,437,032 discloses a sensor for performing distance measurements using ultrasonic echo principles in order to detect and display the approximate distances between a motor vehicle and obstacles in the vicinity of the vehicle. The sensor includes an ultrasonic transmission and reception transducer for transmitting ultrasonic signals and receiving ultrasonic signals reflected by the obstacles. The transducer consists of an insulating material and piezoceramic oscillators.
German Offenlegungsschrift No. 42 01 806 discloses a reversing aid for automobiles which uses ultrasonic waves to measure the distance between a vehicle and an obstacle behind it. The ultrasonic emitters which emit ultrasonic pulse and the electroacoustic transducers which receive the ultrasonic waves reflected by the obstacles are inlaid in flexible plastic plates. These plates are positioned on the left and right rear fenders of the vehicle. Piezoelectric, magnetostrictive or other ultrasonic emitters can be employed.
U.S. Pat. No. 5,629,690 discloses ultrasonic sensors mounted in corresponding bores in motor vehicle fenders, the bores being oriented in such a way that reflections from the road do not produce interference. Each ultrasonic sensor is provided with a cover such as a strong plastic sheet which is matched to the contour of the outer part of the motor vehicle and may also cover the entire part of the vehicle in which the sensor is mounted.
The prior art arrangements described above have the disadvantage that, because of the small number of sensors provided, it is either impossible to have continuous monitoring of the surroundings or it is necessary to provide mechanical tilting instruments for monitoring the entire surrounding region.
In order to avoid this disadvantage, U.S. Pat. No. 5,572,484 describes an ultrasonic warning system for vehicles which contains a rear transmission and reception arrangement consisting of four discretely arranged transmission and reception units integrated in a hexagonal fender arrangement, and a front transmission and reception arrangement consisting of six more transmission and reception units, likewise discretely arranged and integrated in a front fender. Four of the units in the front of the vehicle are arranged to monitor forwardly of the vehicle and the other two are arranged to monitor the front right and front left comer regions. However, such a large number of sensors involves extensive mounting arrangements and great expense.